It is well known in the art relating to diesel engines to use swirl producing cylinder inlet ports to aid the creation of combustion chamber turbulence for improved mixing and combustion of the injected fuel charge. Recently, increased emphasis has been placed on the use of such swirl producing inlet ports in spark-ignition internal combustion engines to provide increased combustion rates with reduced ignition delay and improved cyclic stability. Such changes have been particularly desirable to offset the effects of reduced compression ratios, retarded spark timing and the use of exhaust gas recirculation as means to control regulated emissions in the exhaust gases.